Step cut "V" osteotomy for acute correction in Blount's disease treatment: A case series.

Introduction: Severe Blount's disease results in progressive multiplanar deformity of the lower limb. There are varus, procurvatum, and internal tibia rotational deformity. Treatment varies for each patient, depending on age, magnitude of deformity, discrepancy, psychosocial factor, and surgeon's experience. The aim of treatment is to acutely correct deformity and realign the mechanical axis. We proposed a technique of step cut "V" Osteotomy which could achieve the aim of treatment safely and effectively.

Methods: Twenty-seven legs from eighteen patients were underwent Step Cut "V" Osteotomy technique in our institution from 2015 to 2017 to produce overvalgus correction. Eleven patients had bilateral deformities, and seven patients had unilateral deformity. All patients had mechanical axis deviation (MAD) away medially to the center of the knee, increase of tibiofemoral angle, and Drennan angle. Outcomes were recorded postoperatively such as infection, compartment syndrome, nerve palsy, range of motion, stability of knee ligaments, union time, early weight bearing and recurrence.

Results: From this Step Cut "V" Osteotomy, we can accurately measure the angle of correction we want to achieve preoperatively. Drennan angle and Tibiofemoral angle (TFA) of the patients improved with subsequent correction of interbal tibia rotation and procurvatum. No complication of compartment syndrome and nerve palsy were found. Patient could perform early mobilization, and weight bearing on second month after surgery because of strong fixation and good ligament stability. No significant postoperative infection occurred. Union time achieved in two to three months, but four legs from patients over 4 years old who underwent surgery experienced a recurrence.

Conclusion: Step Cut "V" Osteotomy is a simple, safe and effective technique for acute correction of severe Blount's disease. And can produce an accurate correction, high union rate and early weight bearing with no complication as a result that would be achieved at the end of treatment.